- Preheat oven to 350 degrees F (180 degrees C).
- Grease a 9x13-inch (23x33-cm) rectangular baking dish.
- In a small bowl, stir together flour, baking powder and salt.
- In another large bowl, with an electric mixer, beat together brown sugar and butter just until combined.
- Add eggs and vanilla and continue beating for another minute or two until creamy.
- Add flour in two or three portions, beating just until combined after each addition.
- Finally, stir in chocolate chips.
- Spread batter in the prepared pan and bake for 20 to 25 minutes or until lightly browned on top and a toothpick poked into the middle comes out clean.
- Cut them into squares after cooling down.